1. Field of the Invention
This invention relates to a piezo-electric resonator installed in electronic equipment, for example, as a reference oscillator or a filter for a microcomputer.
2. Description of the Related Art
In the prior art, a piezo-electric resonator installed in electronic equipment has a fundamental configuration in which a piezo-electric substrate formed with electrodes at its two main planes is held by terminal boards. The terminal boards are formed with resilient projections and the projections are contacted with the piezo-electric substrate composed of a piezo-electric ceramic plate, for example. This piezo-electric ceramic plate and the terminal boards are stored a the case. In the gazette of Japanese Patent Laid-Open No. Sho 61-199313 is disclosed a system in which a plurality of projections are formed at an inner surface of the case. These projections hold non-vibrated sections at outer circumferential side surfaces of the piezo-electric ceramic plates so as to prevent the piezo-electric ceramic plates from being displaced from their set positions under an external application of vibration.
However, since the projections at inner surfaces of the case always contact with the outer circumferential side surfaces of the piezo-electric ceramic plates, a shrinkage of the case due to variation in temperature causes high stress to be applied to the piezo-electric ceramic ates. As a result, an electrical characteristic of the piezo-electric resonator is varied. In addition, when a high shock is applied to an external side to the case, there is a possibility that the piezo-electric ceramic plates may be damaged.